The present invention relates to industrial textiles. More particularly, the present invention relates to industrial textiles assembled from a plurality of pre-crimped components, methods of manufacturing those components and methods of assembling the textiles.
Industrial textiles, such as papermaking, filtration and like fabrics, are commonly assembled from a plurality of thermoplastic monofilament or multifilament yarns. Due to the size of these textiles, the preferred method of assembly is generally to interweave the yarns as warp and weft materials in an industrial loom or similar device. Other assembly methods are also known and used. For example, it is known to assemble papermaking fabrics and conveying belts from a multiplicity of helical coils interdigitated and interconnected by means of inserted pintles or hinge yarns. See U.S. Pat. No. 4,528,236 (Finn et al.). It has also been proposed to manufacture industrial textiles built upon a polymeric grid-like material into which reinforcing yarns are embedded to increase the strength of the grid. See U.S. Pat. No. 4,740,409 (Lefkowitz). It is also known to assemble industrial textiles from one or more strips of woven, knit or nonwoven fabric layers which are spirally wound one over the other and then interconnected by various means. See U.S. Pat. No. 5,268,076 (Best et al.) It has also been more recently proposed, in U.S. Pat. No. 5,879,777 (Shipley) which is commonly assigned to the present assignee, to assemble industrial textiles from smaller strips or panels which include an integral joining means, such as hook-and-loop type fasteners.
Woven fabrics are commonly heat set to fix the component yarns prior to use and permanently set crimp at locations where two or more yarns cross over one another (commonly referred to as xe2x80x9ccrossover pointsxe2x80x9d), and, thereby, stabilize the fabric. The amount of crimp imparted to the yarns at a crossover point is dependent on several factors, including: the tension applied to the warp yarns during weaving, tension applied during heatsetting, the so-called xe2x80x9cbeat-upxe2x80x9d capability of the loom, and the physical characteristics of the yarns (i.e.: their size and material composition).
Generally speaking, relatively larger yarns must be woven at higher weaving tensions than relatively smaller yarns in order to impart the desired crimp during beat-up. The degree to which either warp or weft yarns are crimped can be controlled, to an extent, by the weaver in accordance with the end use requirements of the fabric. However, the physical limitations of this control will be dictated by the physical properties of the warp and weft yarns and the beat-up capability of the loom. For example, in experiments conducted to provide a 100% warp fill papermaking dryer fabric woven using 0.8xc3x971.2 mm rectangular PET weft yarns and 0.33xc3x970.66 mm PET warp yarns at tensions between 550 and 1000 kg/m, it was observed that virtually no crimp was imparted to the large weft yarns following weaving and heatsetting. The fabric had minimal interlocking at the crossover points and was slack and exhibited poor dimensional stability.
In the manufacture of industrial textiles, particularly by weaving, it is frequently desirable to use relatively large diameter yarns, for example yarns having a diameter or thickness of at least 0.8 mm, in either, or both, the warp and weft directions. Large diameter yarns, particularly when used as the weft material in the weaving of papermaking press or dryer fabrics, offer several advantages. Such fabrics can be woven at a low xe2x80x9cknockingxe2x80x9d (number of weft yarns per unit of fabric length) so as to provide a fabric having a relatively high air permeability (economy of manufacture). The resulting fabrics are very stiff in the cross-machine direction, but remain flexible in the machine direction, which is highly desirable in certain applications. It may also be desirable to produce a textile product having a relatively low permeability to air but a high drainage rate for other fluids. However, as previously noted, as the size of the warp or weft yarns increase, the dimensional stability of fabrics in which they are incorporated tends to decrease due to the difficulty of imparting sufficient crimp to the yarns during weaving and/or heat setting. A degree of crimp is necessary to interlock the yarns and stabilize the fabric.
It is also desirable in other applications, such as producing woven or braided strapping or sleeving, to utilize larger diameter yarns or yarns made from heat and/or moisture resistant materials. However, due to the difficulties encountered when attempting to impart sufficient crimp to these yarns during weaving or braiding so as to provide a dimensionally stable textile product, it is frequently not possible to make the desired article. This is also true for brittle or inflexible materials, such as (polyphenylene sulfide) PPS, that has many desired properties, but is not generally amenable to being woven or braided because the yarns tend to crack and break at temperatures normally used for these assembly processes.
It is also necessary in some applications of industrial fabrics, such as papermaking fabrics, to insert stuffer yarns into the open weave to further reduce fabric permeability. However, it is difficult to insert more than one stuffer in a given channel or path through the woven fabric. Often, it is desirable to insert two or more stuffer yarns, which can more easily conform to the available space in the weave, and which could also be made of different materials, rather than a single larger stuffer yarn.
It may also be desirable to impart certain surface characteristics to the belting or fabric so as to emboss or transfer a texture to the product being conveyed. This can be done by applying a liquid polymeric resin to a textile substrate and then curving it provide the desired surface texture. It may also be done by utilizing a weave pattern which creates relatively large floats of the warp and/or weft yarns, leaving empty xe2x80x9cpocketsxe2x80x9d in between. However both methods are relatively costly and, in the former case, requiring an extra process step (or steps) to complete.
It would also be desirable to form belting from polymeric materials, which could be used in various applications, such as tire reinforcement belting, rubber hose reinforcement, or tubing, which has high strength and stability. It is believed that such polymeric belting could be more easily bonded to by rubber compounds, and can provide economy of manufacture over known materials, such as steel belting used in tires.
A need therefore exists for an industrial textile and/or weaving or braiding components for such textiles or industrial articles, such as yarns or strips, which are pre-crimped or thermoformed so as to impart a plurality of dimensioned indentations sized and shaped so as to be substantially complementary to the cross-sectional size and shape of the components with which they will be assembled or mated. Pre-crimping or thermoforming textile components prior to assembly makes it possible to assemble dimensionally stable industrial textiles from yarns or components previously impractical for such applications due to weaving or heat setting difficulties associated with them.
The present invention relates to industrial textiles that are assembled, at least in part, from a plurality of pre-crimped polymeric components, particularly yarns, strips and the like. Crimp is imparted to the components so as to provide dimensioned indentations that will be generally complementary, in shape and size, to the components with which they are to be assembled or mated. The textiles may be assembled by weaving, braiding or a similar process such as mechanical interlacing.